Herson,
I'm sorry to read about your situation with your Mom.
In my humble opinion it sounds to me like your mother has a new cancer unrelated to the cancer in her tongue. I am not an expert, but from what you describe I believe she is fighting a new cancer. I'm sorry that I am not able to help or offer advice in this situation regarding the staging, diagnosis or how it came to be.
I would sugest to keep asking the doctors the difficult questions. Try and get a definitive diagnosis (name the cancer) from them. If you have not already done so, I would suggest trying to find and contact a CCC.
I applaud your selfless efforts that you are putting forth for the mother you love, she is blessed to have you.
My thoughts and prayers are with you and your mother.

Contact me anytime if you feel I can help.

Mike